The monoclonal gammopathies are a group of disorders associated with monoclonal proliferation of plasma cells. The International Myeloma Working Group has reviewed their criteria for diagnosis and classification and also response criteria for multiple myeloma with the aim of producing simple, easily used definitions based on routinely available investigations. The use of these criteria will facilitate comparison of therapeutic trial data in the future.

        Key words: monoclonal gammopathies, multiple myeloma, diagnosis, classification, response criteria.